Dump trailers are employed for hauling loads of bulk products, such as coal, scrap metal, dirt, and the like. Dump trailers are different than regular trailers. as a dump trailer typically includes a hydraulic or pneumatic cylinder that can cause the trailer to pivot between a travel position, wherein the trailer is disposed generally horizontally or parallel to the road surface upon which it is traveling, and a tilted or “dump position” wherein the dump trailer is placed at up to a 45 degree angle to the road surface on which it is traveling. When in the dump position, the trailer is capable of emptying its load from the trailer onto whatever surface is behind the trailer.
Dump trailers typically come in two primary species, including round bottom trailers and square bottom or rectangular cross section or “square bottom” trailers. Examples of round bottom trailers are those manufactured by Alumitech, and also by Mac Trailers. Mac Trailers uses a trailer design that was originally created by the Applicant, and produced by American Trailer Manufacture Co., Inc., of Rockport, Ind. American Trailer manufactures a dump trailer that is designed for being pulled by a semi-tractor. The trailer has a generally hemi-cylindrical shape, so that it has a half-round cross-section. The top of the trailer is open so that bulk load materials such as scrap, coal, dirt and grain can be loaded into the trailer by bucket loaders. Although the trailers come in different lengths, most trailers have a length of between about 24 and 53 feet.
The front of the trailer includes a king pin that is positioned for insertion into a fifth wheel of a semi-tractor. A hydraulic, or pneumatic cylinder is pivotably coupled to the front of the trailer to lift the front end of the bed of trailer upwardly, so that the load in the trailer can be dumped out of a rear-mounted gate of the trailer. A pair of draft arms are disposed under the dump bed, and pivotably connected to the dump bed to provide support for the dump bed as it moved between its down (or travel) position and its raised (or dump) position.
In addition to the half-round trailer produced by American Trailer Manufacturer, other open top trailers existed that are designed for carrying bulk loads, such as square (“Flat”) bottom dump trailers and “hopper trailers”. Hopper trailers are not designed for being tilted like a dump trailer. Rather, hopper trailers include closeable chutes that are formed on the underside of the dump trailer. In order to unload materials from a hopper trailer, the trailer is pulled over a pit-like receiving area, and the chutes are opened to allow the materials within the bed of the trailer to flow through the chutes and into the pit-like receiving area.
Although the above mentioned trailers do perform their respective duties in a workman-like manner, room for improvement exists. Two areas where room for improvement exists relate to: (1) the carrying capacity of the trailer; and (2) the repairability of the trailer.
The load limit of a bulk material containing trailer is usually defined not by volume, but by weight. In many situations, the user cannot fill all available space within a trailer with the “cargo” because to completely fill the trailer would place the trailer and its load above load limits that are permitted by relevant state and federal statutes. As such, many bulk trailers operate at a less-than-full “volumetric load”. While being full from a weight perspective, these loads do not fill the volumetric capacity of the trailer.
Since the trailer is at less than full volumetric capacity, one could increase the volume and weight of cargo carried if one were able to reduce the weight of the trailer, since the load weight of the cargo-carrying trailer is a combined function of the weight of the cargo and the weight of the trailer itself. For example, if the weight of the trailer were reduced by 1000 pounds, the trailer might still have the volumetric capacity to carry an extra 1,000 pounds of cargo while still meeting the federally and state mandated weight load limits.
The price charged by trucking companies for carrying a load is usually a function of both weight and volume. The ability to carry a load that includes 1,000 pounds of additional cargo would enable the trucker to charge additional monies to the shipper. In this regard, the Applicant believes that a weight savings of approximately 1,000 pounds in trailer weight. that enables the user to carry an additional 1.000 pounds of cargo per load would enable the trucker to earn sufficient extra marginal revenue, to pay for the trailer in five years. This is no small feat in view of the fact that trailers such as the ones of the instant invention likely cost somewhere between $40,000 and $50,000.00.
A second problem that exists with current dump trailers relates to repairability. Unfortunately, dump trailers have a tendency to become damaged during use and to have their useful life cut short because of accidents. In addition to the normal type of “on-the-road” accidents that one might expect to encounter due to jack knifing and other accidents, dump trailers are likely to become damaged due to roll overs or turn overs during those times when the dump bed is elevated, and the load is being dumped. Roll overs are often caused during dumping, because the wheels are on uneven terrain during the dump.
Simple notions of physics, torque and high centers of gravity suggest that a trailer has an increased probability of rolling over when it has its rear wheels placed on uneven ground and its dump bed elevated, so that the load is far removed from the pivot point defined by the intersection of the back wheels and the terrain. One might expect that the rollover forces exerted on the lifted dump trailer would not be that great because the load would become dumped out of the trailer as the bed was elevated. However, it often occurs that a load becomes “stuck” in the trailer bed, and does not slide out readily when the dump bed is lifted. As such, the front end of the trailer can be in a position where it is raised a significant (e.g. 20 to 30 feet) distance above the ground, and contains a significant amount of additional weight due all or part of the cargo being still resident in the inside of the trailer bed. Surprisingly, it is estimated that approximately 40% of dump trailers will, at some point during their existence, roll over during some sort of dump accident. When the trailer rolls over, it must either be repaired or become “totaled”.
Typical known prior art dump trailers are comprised of several aluminum or steel sheets that are welded together and welded together and maintained in place by a series of external skeleton members, such as top rails and lower rails, that extend along the length of the trailer. After a roll over, the most typical repair required is to cut out and replace a significant amount of the aluminum sheet that comprises the round or square bed, along with one or more several foot-long sections of rail. It is estimated by the Applicant that a typical roll over will result in somewhere between $15,000.00 and $25,000.00 of damage inflicted upon the trailer. To place this in perspective, this $15,000.00 to $25,000.00 constitutes somewhere approximately between 30% and 60% of the cost of a new $45,000.00 trailer.
It would be beneficial to provide a trailer that was capable of being repaired less expensively in the case of such a roll over accident. Therefore, one object of the present invention is to provide a trailer that has a greater potential to have a lighter weight than current known trailers. It is also an object of the present invention to provide a trailer that has a potential to have lower repair costs than currently known trailers.